Highly Filled Aluminum Paste for PERC Point Contacts
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Solution Overview
Problem
Conventional aluminum pastes for point contact aluminum back surface field structures in PERC cells suffer from poor filling capacity, cavity formation, and damage to passivation films, leading to suboptimal ohmic contact and reduced photovoltaic conversion efficiency.
Innovation Solution
A highly filled back surface field aluminum paste comprising 70-85% aluminum powder, 1-5% nanosized aluminum-boron-antimony alloy powder, 10-25% organic carrier, 0.1-6% inorganic binder, and 0.01-1% auxiliary additive, with the alloy powder enhancing wettability and thermal stability, is developed to achieve a filling ratio of over 90% and minimize film damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional aluminum paste is used for point contact aluminum back surface field structures, then the manufacturing process is simple, but the filling capacity is poor and cavities are formed
Solution Approach 1:
The patent uses composite aluminum powder consisting of aluminum powder with particle size of 5-20 μm and nanosized aluminum-boron-antimony alloy powder (average particle size 20-80 nm) in a weight ratio of 95:5 to 90:10. This composite material structure combines the filling capability of larger particles with the flowability and cavity-reducing properties of nanosized particles, achieving over 90% filling ratio while maintaining processability.
Solution Approach 2:
The patent modifies the particle size distribution parameters of the aluminum powder by introducing nanosized alloy powder (20-80 nm) alongside conventional aluminum powder (5-20 μm). This parameter change in particle size distribution improves the paste's ability to fill point contact structures completely, eliminating cavities and achieving high filling capacity.
2Reliability
If conventional aluminum paste is used, then the paste formulation is simple, but the ohmic contact quality is poor due to cavity formation
Solution Approach 1:
The patent introduces nanosized aluminum-boron-antimony alloy powder (20-80 nm) that preferentially fills cavity regions and interfaces between aluminum particles and silicon substrate. The boron and antimony elements locally enhance wettability and electrical contact quality at critical interfaces, ensuring reliable ohmic contact while maintaining overall paste composition balance.
3Object-affected harmful factors
If conventional aluminum paste is used, then the application process is straightforward, but the passivation film is severely damaged
Solution Approach 1:
The patent modifies the chemical composition parameters of the aluminum powder by incorporating nanosized aluminum-boron-antimony alloy powder. This parameter change reduces the erosion aggressiveness of the paste toward passivation films during application and sintering, protecting the back surface field passivation film while maintaining effective aluminum contact formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The paste forms a uniform and dense back surface field layer with high filling ratio, reducing cavity formation and improving ohmic contact, thereby enhancing the electrical performance and photoelectric conversion efficiency of PERC silicon solar cells.
Implementation Method 1
The existence of boron and antimony in the nanosized aluminum-boron-antimony alloy powder makes the glass powder has good wettability
Implementation Method 2
cannot form good ohmic contact with silicon substrate after being sintered
Implementation Method 3
The filling ratio is more than 90% with the use of the aluminum paste in the invention
Data Source
AI summary
A highly filled back surface field aluminum paste for point contacts in PERC cells and its preparation method include dissolving ethyl cellulose in organic solvent, stirring under a certain temperature to prepare a homogeneous and transparent organic carrier, adding aluminum powder, nanosized aluminum-boron-antimony alloy powder and auxiliary additive, and three-roller grinding, comprising 70-85 parts by weight of aluminum powder, 1-5 parts by weight of nanosized aluminum-boron-antimony alloy powder, 10-25 parts by weight of organic carrier, 0.1-6 parts by weight of inorganic binder and 0.01-1 part by weight of auxiliary additive.